Dissertations, Theses, and Capstone Projects

Date of Degree

2-2019

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biochemistry

Advisor

Yujia Xu

Committee Members

Rein Ulijn

Mandë Holford

Peter Lipke

Shuiqin Zhou

Subject Categories

Biochemistry

Abstract

We recently reported that a designed triple helix Col108 self-associates to form collagen-like mini-fibrils having a d-periodicity of 35 nm. Recombinant protein Col108 consists of 378-residue triple helix domain organized into three repeating sequence units, and a C-terminal foldon domain. The 35 nm d-period of Col108 mini-fibrils is consistent with the one unit staggered arrangement of the associating helices. To further investigate if the sequence periodicity is crucial for collagen mimetic peptide fibril formation, we studied the self-assembly of four other designed triple helical peptides. Peptide 2U108 has two repeating sequence units; peptide Col877 consists of three repeating units but the amino acid sequence of each unit is very different from that of Col108; peptide 1U108 has only one sequence unit and peptide. Col108r has the same amino acid composition of that of Col108 but lacks the sequence periodicity. Both 2U108 and Col877 formed mini-fibrils having the same periodicity of 35 nm as that observed in Col108 under electron microscopy, but no fibril-like assemblies were observed for either 1U108 or Col108r. Since both 2U108 and Col877 have tandem repeats of sequence units while 1U108 and Col108r do not, these findings support the essential roles of the long-range repeating sequence units on the self-assembly of collagen-like, staggered fibrils and suggest a design-rule for the self-assembly of triple helices into collagen-like mini-fibrils.

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